1. Field of the Invention
The present invention relates generally to an internal combustion engine and more specifically to an induction sensor arrangement for a fuel injected engine or the like which enables accurate derivation of the amount of air inducted thereinto without the need for excessively large amounts of pre-memorized data.
2. Description of the Prior Art
In order to optimally control fuel injected engines it is vital to accurately sense the amount of air being inducted into the engine. To achieve this there are two basic types of air induction sensor arrangements: (a) those which sense the amount of air being inducted directly and (b) those which derive the same indirectly using two or more related parameters.
Hotwire/vortex and flap type air flow sensors fall into the first category. However, these sensors tend to be overly responsive to the pressure pulsations which occur in the induction system and thus suffer from the drawback that their accuracy is apt to vary widely depending on the mode of the operation of the engine. This induces the drawback that, as the amount of fuel supplied to the engine is determined using the sensed induction volume, the torque generated by the engine tends to undesirably fluctuate with the accuracy of the induction system.
In the case of indirect sensing, it is known to combine the engine rotational speed, the output of a pressure sensor which detects the pressure in the induction manifold and the output of a throttle valve position sensor.
However, in order to cover all of the possible parameter combinations and thus enable a good matching of the amount of fuel injected with the instant mode of operation over the whole range of engine operation, it is necessary to record a vast amount of data in the form of a four parameter system (or systems) wherein each value of one parameter has three corresponding values which define its position in a three-dimensional lattice, namely, record tables which can be depicted in the form of (three dimensional) contour maps. This requires a large amount of memory space (ROM) and increases the cost of the system. One solution to this problem is to reduce the amount of data which is recorded by increasing the increments between each of the recorded values (viz., reduce the resolution of the mapping). However, this tends to cause the control of the system to become overly coarse and deteriorates the accuracy of the same.
The above mentioned memory problem is further aggrevated when the engine is provided with a swirl control arrangement. Viz., as the swirl control valve effects the effective cross sectional area of the induction conduit the accuracy of the derivation possible using only the above mentioned parameters is severely jeopardized. Accordingly, in order to take this effect into consideration an additional large amount of data is required.